A series of novel t-butyl group-containing poly(amide-imide)s IIIa-m were synthesized by the direct polycondensations of 1,4-bis(4-aminophenoxy)-2-t-butylbenzene (BAP-tBB) with various aromatic bis(trimellitimide)s IIa-m in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Poly(amide-imide)s III having inherent viscosities between 0.67 and 1.77 dl g(-1) were obtained in quantitative yields. Most of the resulting polymers were readily soluble in polar solvents such as NMP and N,N-dimethylacetamide. All of the soluble poly(amide-imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of the-se polymers were in the range of 243-300 degrees C, and the 10% weight loss temperatures were above 490 degrees C in nitrogen. The properties of poly(amide-imide)s III were compared with those of the corresponding poly(amide-imide)s III' prepared from the bis(trimellitimide) of BAP-tBB and various aromatic diamines. (C)2000 Elsevier Science S.A. All rights reserved.